The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art, or relevant, to the presently described or claimed invention, or that any publication or document that is specifically or implicitly identified is prior art or a reference that may be used in evaluating patentability.
Over the course of time there has been disclosed many different types of apparatus for facilitating the formation of yarn. For example, reference may be made to U.S. Pat. No. 5,765,353 by Roland et al. which describes an apparatus for pot spinning of yarn that generally comprised a spinning pot rotatable about a spinning axis for formation of a yarn cake on an inner circumferential surface of the spinning pot, a tubular yarn guide having an exit mouth for delivering a yarn into the spinning pot in the form of a traveling extent of the yarn revolving about the axis of the spinning pot, and means for monitoring deviations in the delivery of the yarn, the monitoring means including means for detecting a duration of revolution of the traveling yarn extent at the mouth of the yarn guide tube.
More particularly by referring to the drawings and detailed description of the Roland et al. patent, there is disclosed a condensing zone which is followed by a pot spinning station. There is a multiplicity of pot spinning stations mounted along a pot rail which contains the drive for the respective pots. However, each pot spinning station has a spinning pot. In this regard, the spinning pot rotates about its center axis to spin and twist the condensed and compacted network of fiber from the condensing zone and form a yarn. The yarn passes through a tubular yarn guide which extend into the spinning pot and emerges from an exit mouth to form yarn extent. When the spinning pot rotates, the yarn extent extends laterally toward and revolves in the direction of rotation of the spinning pot under the centrifugal influence of the rotating spinning pot. Accordingly, the yarn is thereby applied and joined to a yarn cake. It is also disclosed that during the spinning operation, the yarn guide moves up and down and then the yarn cake forms progressively on an inner circumferential wall of the spinning pot 81.
Another type of apparatus for facilitating the formation of yarn is disclosed in U.S. Pat. No. 6,134,872 by Olbrich. The Olbrich patent describes an apparatus for making a compacted yarn that generally comprises a drafting frame for drafting a fiber strand to produce a fiber ribbon; means along a path of the fiber strand in the drafting frame and including a surface formed with a perforation to which a suction can be applied for compacting the fiber ribbon; a suction device is connected to the perforation for evacuating a suction air stream through the perforation to form from the fiber ribbon a transversely compacted strand of fibers; means for imparting a twist to the compacted strand; means for monitoring the suction air stream at at least one location for generating an indication of a monitored parameter of the suction air stream falling below a threshold valve; and means for outputting a signal in response to such an indication which signal can be used for shutdown or for altering personnel. This apparatus thus results in the elimination of the reduction in yarn quality which can occur when the compaction system becomes blocked by lint, fiber accumulation or the like.
More particularly, by referring to the drawings and the detailed description of the Olbrich patent there is disclosed a fiber condensing zone equipped with a compact spinning device is provided in the downstream of a second pair of rollers. In the condensing zone a stretched and broken network of fiber is drawn together toward the center thereof and then is condensed or compacted. The condensing zone is provided with a suction device with a perforated belt guided around an upper roller of an intake roller pair. The perforations in the belt include a row of small orifices disposed one by one, extending in a row in the travel direction of the network of fibers. The perforated belt passes around a belt cage and the perforated belt is driven. A belt cage is connected by a suction pipe to a suction generating device to form a suction unit. Through the suction unit, a suction air stream is generated which serves to condense and compact the network fiber toward the center thereof. After the condensed and compacted network of fiber leaves an intake pair of rollers, a twist can be imparted to it through the operation of a ring-spinning station or pot spinning station. An upper roller can be mounted on a weight arm so that it can weigh against a lower roller and so that it can be driven.
In another embodiment in the Olbrich patent an upper roller is mounted together with a lower roller on a separable compact spinning device. The compact spinning device in this embodiment is equipped with a perforated belt and a total suction unit. The lower roller is driven by a drive roller, and then it drives the upper roller to rotate simultaneously. The compact sinning device is mounted into a condensing zone to condense and compact the stretched and broken network of fiber from a second pair of rollers.
In yet another embodiment in the Olbrich patent a condensing device generally comprises a drum roller. The drum roller is provided with a row of orifices along a center line. The drum roller is thus a perforated suction drum roller. When the network of fiber from a second pair of rollers passes through, the drum roller rotates against it on two counter rollers to condense and compact it. The suction stream is applied through a suction pipe to the drum roller. After the condensed and compacted network of fiber leave the drum roller, a twist can impart to it through the operation of ring-spinning station or pot spinning station.
In the Olbrich patent, all of the disclosed embodiments of compact spinning devices have the same feature of condensing or compacting the network of fibers with a surface formed with perforations and applying suction to the perforations by evacuating a suction air stream through the perforations to form a condensed and compacted network of fibers.
Turning now to developing a better understanding of the present invention, it can be noted that a fire retardant is a substance that helps to delay or prevent combustion. See Horrocks, A. R., Fire Retardant Materials (2001). Fire retardant clothing, for example, is widely used to protect persons who are exposed to fire, particularly suddenly occurring and fast burning conflagrations. These include persons in diverse fields such as race car drivers, military personnel and fire fighters, each of which may be exposed to deadly fires and extremely dangerous incendiary conditions without notice. For such persons, the primary line of defense against severe burns and even death is the protective clothing worn over some or all of the body.
Materials such as carbon-based fiber materials and aramid fiber materials have been used to form fire retardant materials for the manufacture of clothing. Carbon-based fibers are typically in the form of long bundles of linked graphite plates that form a crystal structure lying parallel to the fiber axis. Carbon fibers, which especially refer to carbon-based fiber materials with higher carbon content about 95% carbon, are anisotropic and their elastic modulus is higher in the direction of the axis than it is in other directions. In other words, the individual fibers can withstand pulling, i.e., they can stretch before breaking, in the axial direction to a greater extent than they can withstand bending at an angle to the axis or lateral stretching. Most carbon fiber materials are made from thousands of individual filaments and include thousands of fibers.
Carbon fiber materials have advantageous mechanical, physical and chemical properties. In addition to being nonflammable, they are light, stiff and strong. The strength of a carbon fiber is comparable to that of steels and the stiffness of carbon fibers is generally greater than metal, ceramic or polymer-based materials. Carbon fibers have other desirable properties such as excellent corrosion and fatigue resistance and dimensional stability. Carbon fibers and their composites are therefore well suited for applications in which chemical inertness, strength, stiffness, lightness, and fatigue resistance are important requirements. For example, in the aerospace and defense industries, materials made of carbon fibers have been increasingly used both in the interior of aircrafts as flame resistant materials and as critical structural components to increase fuel efficiency and enhance structural strength.
Carbon-based fiber materials with lower carbon content about 55-68% carbon may be advantageously combined with further materials to form yarns, fabrics or other products that exhibit the advantageous qualities of both the carbon-based fiber materials and the further material. The carbon-based fibers may be combined with other materials at the yarn level to form a yarn having characteristics of both carbon-based fiber and the other additive material. Such may be a blended yarn. Carbon-based fibers may also be formed into a fabric that is used in conjunction with other fabrics to impart the desired combination of characteristics.
Carbon-based fibers may be produced from a variety of precursor materials. Among these precursor materials are polyacrylonitrile (PAN), petroleum or coal tar pitch and certain phenolic fibers. Cellulosic fibers such as rayon and cotton may also be used as additives. Different precursor materials produce carbon-based fibers with different morphologies and different specific characteristics. PAN-based carbon-based fiber materials exhibit superior tensile strength, are comparatively low in cost, and are well suited for use in the construction of consumer goods such as sporting goods and high-performance apparel.
Various methods are known for producing carbon-based fibers from various precursor materials. Such methods include pyrolytic processes and pyrolysis. It is well established that the mechanical properties of carbon-based fibers are improved by increasing their crystallinity and the molecular order within the fiber. One way to increase crystallinity and structural order is through a process of stabilization and carbonization through tension. One common pyrolysis reaction is an oxidative stabilization process in which a precursor fiber is treated at about 200-300.degree. Centigrade under tension in an oxidizing environment. During the process, oxygen, nitrogen and/or hydrogen is removed from the fiber, resulting in an increase of carbon content in the fiber. In addition to preventing fiber shrinkage, the tension applied during this process maintains the molecular orientation and order of the fiber, which in turn increases the tensile strength of the stabilized fiber.
During pyrolysis of PAN, the oxidation and stabilization induces intramolecular cyclization of the oriented molecules with the release of most of the hydrogen and part of the nitrogen from the fibers. The resulting PAN polymers are called “oxidized PAN” and oxidized PAN typically has a carbon content of about 55-68% and a density of about 1.30 to 1.50 g/cm.sup.3. Oxidized PAN fibers have several advantages as flame resistant materials. Oxidized PAN fibers exhibit excellent heat insulation properties and low thermal conductivity. Oxidized PAN fibers also have a high limiting oxygen index (LOI), typically between 40-60% oxygen making them more flame resistant than many other organic fibers. Moreover, textiles that include strands of oxidized PAN fibers, unlike other flame resistant organic fibers, retain their appearance and textile characteristics after open flame exposure. Oxidized PAN fibers are electrically nonconductive and function as effective electrical insulators even after exposure to heat and open flames. Oxidized PAN fibers also exhibit excellent chemical resistance to organic solvents and most acids and bases. Moreover, oxidized PAN fiber strands are softer, more pliable and malleable than strands of pure carbon fibers. As such, oxidized PAN fiber strands are well suited for use in heat resistant thermal insulations and textiles for high technology applications, either alone or as part of a composite material, and have been used in composite fire blocking fabrics for seating in the aerospace and automobile industries and in the manufacture of composite fire retardant and protective clothing for people exposed to the danger of an open flame.
Currently, there are at least three types of oxidized PAN materials available commercially: staple fibers, large filament tow materials, and small filament tow materials. In using these materials in the production of composite industrial and consumer products, the staple fibers and large filament tow materials are often spun into yarn using complex, multi-step processes that commonly include, for example, the addition of strengthening fibers to the carbon-based fiber material, or the addition of laminate coatings to fabrics that they are used to prepare.
For staple fibers, relatively short natural or synthetic fibers, the first step in the production of yarn is “carding”, in which the fibers are opened and combed over cylinders that contain extremely fine wires or aligned teeth. The fibers are then aligned in one direction to form a large loosely assembled but not twisted continuous strands of fibers known as “sliver”. Several strands of sliver are then drawn multiple times onto drawing frames to further align the fibers to improve uniformity as well as to reduce the diameter of the sliver. The drawn sliver is then fed into a roving frame to produce “roving” by further reducing the diameter and imparting a slight false twist. Finally, the roving is fed into a spinning (i.e., winding and/or twisting) frame where it is spun into yarn.
For large filament tow, the first step is different, and consists of a stretch-breaking process in which the large tow is broken into multiple fragments and aligned into sliver. The sliver is then further processed as described above. These processes are laborious, inefficient and costly, require as many as 6 or 8-12 separate steps and often require the use of more than one type of apparatus.
It would be desirable to provide an economical process for converting oxidized PAN materials into yarn using a reduced and minimum number of operations. It would also be desirable to produce an economical process for converting other starting material into yarn using a reduced and minimum number of operations. It would be particularly advantageous to provide a single process that could be used to convert various different materials into yarn. It would be further desirable to provide a process for converting oxidized PAN materials or other starting materials into yarn using a single apparatus. It would be further desirable to provide a process and apparatus for converting multiple starting materials into yarn simultaneously and in particular to produce a blended yarn by combining the multiple starting materials. It would be further desirable to provide a process and apparatus for converting one or multiple starting materials and one or multiple yarns into a twisted yarn simultaneously and in particular to produce a core yarn by combining and twisting one or multiple cohesive elongated network of fibers of starting materials and one or multiple yarns.
Oxidized PAN materials provide superior fire retardant and heat resistant qualities, i.e., a high LOI and superior Thermal Protective Performance, TPP, but when they are formed according to conventional methods, the strands formed from oxidized PAN fibers are typically brittle, weak and prone to abrasion and cutting. Yarns formed from pure oxidized PAN using conventional methods exhibit undesirably low cut resistance, abrasion resistance and tensile strength and do not include sufficient tensile strength to be knit or woven into fabrics. As such, fabrics made from oxidized PAN fiber strands using conventional methods typically include the fire retardant and heat resistant oxidized PAN strands in combination with one or more high strength or strengthening filaments/fibers. Aramid fiber is an example of such a strengthening filament. The strengthening, filaments/fibers in combination with the oxidized PAN produces a fibrous blend having improved tensile strength, cut resistance and durability but the additives, i.e., the strengthening fibers, compromise the flame retarding and heat resisting properties of the fabric.
It would be desirable to produce a yarn and textile and other materials that are composed entirely of oxidized polyacrylonitrile fibers or carbonized polyacrylonitrile fibers yet exhibit sufficient tensile strength to be knittable. It would also be desirable to manufacture an intermediate product that may be used to produce such yarns and textile and other materials. It would also be desirable to combine such an intermediate product to produce blended yarns or textiles.